This duct was never hooked up to o the air register.
It is the latest thing in HVAC, it is Wireless/Bluetooth.
Deal Killer.:D:D Nice Catch
I check each register with a IR thermometer, looking for that. I find it periodically.
See now HVAC guys here only check at the supply plenum. This means they would never catch that problem. This is why checking at the supply registers for temp differences is a big thing. I always get into arguments with HVAC contractors about this exact thing.
That is why I take plenty of pictures. They cannot refute it and it makes it easy for them to find.